A purified protein from the coelomocytes of the sea star Asterias forbesi has many of the biological properties of lymphokines produced by T lymphocytes. This sea star factor (SSF) has been demonstrated under appropriate conditions to either stimulate or suppress T lymphocyte function, to activate macrophages and to have a cytostatic action on tumor cells. We propose to systematically determine the optimal conditions for the use of SSF used alone or with other agents in producing transplantation immunity to syngeneic rodent tumors. Accomplishment of this objective will allow us to examine the effectiveness of SSF used alone or in combination with other agents in animal immunotherapy models designed to approximate several clinical situations. We also wish to explore the use of SSF in producing in vitro anti-tumor sensitization. In addition we wish to explore the optimal conditions for the use of SSF used alone or with other agents in preventing or treating graft-versus-host reactions.